This invention relates to improvements in ball valves. More specifically, the invention relates to a ball valve structure in which at least one seal of the valve is releasably held in place by mounting same on a removable seal insert which is held in place in the valve body by a special locking element.
Ball valves are very well known in the art as effective means for controlling the flow of fluid. Such valves generally comprise a rotatable spherical ball located in a chamber within the valve body. A fluid passageway through the ball permits the flow of fluid through the valve when the ball is in an open position. Ideally, when the ball is in the closed position leakage of fluid through the valve is prevented. This requires the use of washers, gaskets, O-rings and other sealing arrangements which contact the ball and the interior wall of the valve body to provide a tight, substantially leak-proof fit of the ball when the valve is closed.
These sealing systems are subject to wear because of contact with the movable ball, damage from exposure to extremes of temperature and pressure, or contact with harmful chemicals passing through the valve. Therefore, periodic maintenance of the sealing systems must be performed.
It is known in the art to provide ball valve seals on opposite sides of the ball and adapted for sealingly contacting the ball in the open and closed positions thereof. One or both of the seals is provided on a hollow cylindrical seal carrier which is removable from the valve body. It is necessary to be able to assemble the valve with the ball already located inside the valve body and to be able to adjust the sealing pressure of the seals on the ball. In some constructions, the seal carrier is glued in place in the valve body, but such a construction is not readily adjustable. In other constructions, the seal carrier or a lock ring therefor, is screwed into the valve body. The screwed-in constructions cannot be adjusted when the valve union is in place. Also, the screwed-in constructions are not as safe as is desired. If the nut of the union is removed from the valve body while the ball valve is closed and is still under pressure, the pressure of the fluid presses the ball axially against the threads. This pressure can destroy the screw connection and cause the seal carrier and the ball to be blown out of the valve body, with possibly serious consequences. In another construction, the removable seal carrier is held in place against the ball and the interior wall of the valve body by means of a bayonet-type mount. A bayonet-type mounting system typically involves one or more pins or other projections extending radially from the seal carrier which are received in one or more grooves on the interior wall of the valve body when the carrier is rotated. Such a bayonet-type mount has various drawbacks which reduce its utility, namely: bayonet-type mounts can, at the most, provide a surface engagement area of only about 50% of the circumference of the valve body and bayonet-type mounts can cause mistakes in use because sometimes it is difficult to ascertain whether the pin-carrying seal carrier has been completely turned so as to be fully engaged and releasably locked in place.